At initiation of a wireless communication session between a wireless transmit/receive unit (WTRU) and a core network, the WTRU requests for a signaling connection in an attach procedure according to third generation partnership project (3GPP) standards. Currently, a network capability to support a short message service (SMS) via dedicated channels and global packet radio service (GPRS) channels are reported in a network capability information element (IE).
However, there is no means for reporting WTRU SM capability via an IMS. As a consequence, the core network is unaware of the WTRU SM capability and an SM may not be routed to the WTRU via an IMS. Since the current wireless communication standards mandate that the WTRU indicate the preferred mode of operation (in terms of delivery of SMS), the WTRU should indicate the delivery of SMS over a GSM network or a GPRS based network. However, for example, if the WTRU is operating on a GPRS network and the preferred setting is on a GSM network, SMS messages may be lost. The same problem also occurs when the WTRU operates in a GSM mode while the preferred operation is GPRS delivery. Therefore, it is desirable to provide a means for the WTRU to report the SM capability over the IMS to the core network.